This invention relates to snap action electrothermally actuated circuit breakers. More particularly, the invention relates to improved circuit breaker mechanisms for use in compact snap action breakers combining the functions of switches and circuit breakers.
A compact snap action circuit breaker is disclosed in U.S. Pat. No. 2,911,503 issued Nov. 3, 1959 to Helmut Garbers. Garbers discloses a safety switch which, in the ON or CLOSED position, establishes a circuit through a bimetallic element, a pair of contacts, and a lever. When the bimetallic element is heated by an overcurrent, it deflects the lever past the center line of an overcenter spring. The switch then snaps open.
In circuit breakers such as disclosed by Garbers, however, the bimetallic elements are generally suspended in air. Reactive elements, therefore, tend to bend the bimetallic element downward, in the opposite direction to that required for tripping of the circuit. Furthermore, breakers such as described in the Garbers patent use separate heater and heating elements to heat the bimetal. Finally, in known circuit breakers, adjustment of the breaker is usually made via an imprecise calibration screw.